CN113767714A

CN113767714A - Robust beam failure recovery procedure for using non-serving cells

Info

Publication number: CN113767714A
Application number: CN202080032814.7A
Authority: CN
Inventors: A·阿瓦达; T·科斯凯拉; J·凯科南; I·维林
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2019-05-02
Filing date: 2020-04-29
Publication date: 2021-12-07
Also published as: EP3964025A1; US11956683B2; WO2020222144A1; US20220174567A1

Abstract

In response to a beam failure being detected for a serving cell serving the user equipment, the UE determines whether a timer is running. Performing, by the UE, one of: a beam failure recovery procedure with a target non-serving cell running in response to a timer; or in response to a beam failure recovery procedure with the serving cell in which the timer is not running. Methods, apparatus, computer programs and computer program products are disclosed.

Description

Robust beam failure recovery procedure for using non-serving cells

Technical Field

The present invention relates generally to mobility procedures for handover of user equipment in wireless networks, and more particularly to beam failure recovery for non-serving cells.

Background

This section is intended to provide a background or context to the invention that is disclosed below. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented, or described. Thus, unless expressly indicated otherwise herein, what is described in this section is not prior art to the description in this application and is not admitted to be prior art by inclusion in this section. The abbreviations that may be found in the specification and/or in the drawings are defined below, at the beginning of the detailed description section.

One of the main goals of the New Radio (NR) Work Item (WI) with respect to mobility enhancement for rel.16 is to study and specify solutions for fast handover failure recovery. See "New WID: NR mobility enhancements" by Intel corporation at RP-181351 meeting #80 at 3GPP TSG RAN in Lahoo, USA, between 21.5.2018 and 25.5.5.4. One of the goals of the WI is as follows:

study solution(s) to improve the reliability and robustness of HO/SCG changes, especially considering the challenges in terms of high/intermediate frequencies, focusing on the solutions identified below, but not limited thereto.

o conditional switch

o fast switching failover "

Therefore, solutions will be investigated to improve Handover (HO) or Secondary Cell Group (SCG) change reliability and robustness. One area of improvement is the triggering of a Beam Failure Recovery (BFR) procedure, which is initiated after a User Equipment (UE) detects a beam failure.

Disclosure of Invention

This section is intended to include examples and is not intended to be limiting.

In an exemplary embodiment, a method is disclosed that includes determining, by a user equipment and in response to a beam failure being detected for a serving cell serving the user equipment, whether a timer is running. The method further comprises performing, by the user equipment, one of: a beam failure recovery procedure with a target non-serving cell running in response to a timer; or in response to a beam failure recovery procedure with the serving cell in which the timer is not running.

Additional exemplary embodiments include a computer program comprising code for performing the method of the preceding paragraph when the computer program is run on a processor. A computer program according to this paragraph, wherein the computer program is a computer program product comprising a computer readable medium bearing computer program code embodied therein for use with a computer. Another example is a computer program according to this paragraph, wherein the program is directly loadable into the internal memory of the computer.

An example apparatus includes one or more processors and one or more memories containing computer program code. The one or more memories and the computer program code configured to, with the one or more processors, cause the apparatus to perform operations comprising: determining, by the user equipment and in response to the beam failure being detected for a serving cell serving the user equipment, whether a timer is running; and performing, by the user equipment, one of: a beam failure recovery procedure with a target non-serving cell running in response to a timer; or in response to a beam failure recovery procedure with the serving cell in which the timer is not running.

An exemplary computer program product comprises a computer-readable storage medium bearing computer program code embodied therein for use with a computer. The computer program code includes: code for determining, by the user equipment and in response to a beam failure being detected for a serving cell serving the user equipment, whether a timer is running. And code for performing, by the user equipment, one of: a beam failure recovery procedure with a target non-serving cell running in response to a timer; or in response to a beam failure recovery procedure with the serving cell in which the timer is not running.

In another exemplary embodiment, an apparatus comprises: means for determining, by the user equipment and in response to a beam failure being detected for a serving cell serving the user equipment, whether a timer is running; and means for performing, by the user equipment, one of: a beam failure recovery procedure with a target non-serving cell running in response to a timer; or in response to a beam failure recovery procedure with the serving cell in which the timer is not running.

Drawings

In the drawings:

FIG. 1 is a block diagram of one possible and non-limiting exemplary system in which exemplary embodiments may be practiced;

FIG. 2 depicts an exemplary signaling diagram of a situation where a beam failure has been detected while the timer T is running;

fig. 3 depicts a situation where a beam failure is detected when the entry condition for a measurement event is being evaluated or even satisfied by the UE but is not satisfied during the TTT; and

fig. 4 is a logic flow diagram of an exemplary process performed by UE 110 for robust beam failure recovery using non-serving cells.

Detailed Description

The following abbreviations that may be obtained in the specification and/or the drawings are defined as follows:

3GPP third generation partnership project

5G fifth generation

5GC 5G core network

AMF access and mobility management functionality

BFD-RS beam fault detection reference signal

BFR beam failure recovery

BFRR beam failure recovery request

BFI beam failure examples

BLER Block error Rate

BS base station

CBRA contention-based random access

CE control element

CFRA contention-free random access

CORESET control resource set

C-RNTI cell radio network temporary identifier

CSI-RS channel state information-reference signal

CU Central Unit

DMRS demodulation reference signals

DU distributed unit

eNB (or eNodeB) evolved node B (e.g., LTE base station)

EN-DC E-UTRA-NR double ligation

EN-gNB or En-gNB provides NR user plane and control plane protocol termination to the UE

And acting as a node of an auxiliary node in an EN-DC

E-UTRA evolved universal terrestrial radio access, LTE radio

Access technology

gNB (or gNodeB) for a 5G/NR base station, i.e. providing NR to a UE

The user plane and control plane protocols terminate and are via NG

Node interfacing to 5GC

MR measurement reporting

NS non-service

HO handover

I/F interface

The first (e.g., lowest) layer in the Ll protocol stack, e.g.,

physical layer PHY

Second (higher) layer in the L2 protocol stack, e.g. MAC, RLC

And/or PDCP

Third (higher) layer in the L3 protocol stack, e.g. RRC, NOT

Access stratum and/or internet protocol

LTE Long term evolution

MAC medium access control, also a layer in the protocol stack

MME mobility management entity

NG or NG next generation

NG-eNB or NG-eNB Next Generation eNB

NR new radio

N/W or NW network

OOS out of sync

PCI physical cell identity

PDCCH physical downlink control channel

PDCP packet data convergence protocol

PHY physical layer

Physical Random Access Channel (PRACH)

RAN radio access network

QCL'd quasi co-site

RA-RNTI random access radio network temporary identifier

Rel version

RLC radio link control

RLF radio link failure

RRH remote radio head

RRC radio resource control

RS reference signal

RU radio unit

Rx or RX receiver or reception

SCG Secondary cell group

SDAP service data adaptation protocol

SGW service gateway

SMF session management function

SSB SS/PBCH block

SS/PBCH Sync Signal/physical broadcast channel

TCI transport configuration indication

TS technical Specification

TTT time of trigger

Tx or TX transmitter or transmission

UE user equipment (e.g., wireless, typically mobile device)

UPF user plane functionality

WI work item

The word "exemplary" is used herein to mean "serving as an example, instance, or illustration service". Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described in this detailed description are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and do not limit the scope of the invention which is defined by the claims.

The exemplary embodiments herein describe a process for robust beam failure recovery using non-serving cells. Additional description of these techniques is presented after describing the system in which the exemplary embodiments may be used.

Turning to fig. 1, a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments may be practiced is shown. A serving Base Station (BS) or cell 170-1, a target non-serving BS or cell 170-2, and network element(s) 190 are illustrated as part of the wireless communication network 100. In fig. 1, a User Equipment (UE)110 is in wireless communication with a wireless communication network 100.

The UE is wireless, typically a mobile device that may access a wireless communication network. UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected by one or more buses 127. Each of the one or more transceivers 130 includes a receiver Rx 132 and a transmitter Tx 133. The one or more buses 127 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, an optical fiber, or other optical communication device, and so forth. One or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123.

UE 110 includes mobility module 140, and mobility module 140 includes portions of one or both of 140-1 and/or 140-2, which may be implemented in a variety of ways. The mobility module 140 may be implemented in hardware as a mobility module 140-1, such as part of one or more processors 120. The mobility module 140-1 may also be implemented as an integrated circuit or by other hardware, such as a programmable gate array. In another example, the mobility module 140 may be implemented as a mobility module 140-2, which is implemented as computer program code 123 and executed by the one or more processors 120. For example, the one or more memories 125 and the computer program code 123 may be configured to, with the one or more processors 120, cause the user equipment 110 to perform one or more operations as described herein. UE 110 communicates with serving BS/cell 170-1 via wireless link 111-1 and with target non-serving BS/cell 170-2 via wireless link 111-2.

Note that there may also be zero, one, or multiple non-serving (NS) BSs/cells 171. If there are one or more non-serving BSs/cells, the set of non-serving cells 172 includes the target non-serving BS/cell 170-2 and X non-serving BSs/cells 171, where X is one or more. The target non-serving BS/cell 170 is a non-serving cell in the set 172 that meets criteria for handover, for example.

A protocol stack 10 is also shown in the UE 110 and is implemented in the computer program code 123 (although the protocol stack 10 may alternatively or additionally be implemented in the one or more processors 120). The protocol stack 10 has a plurality of layers 20: l120-1, a first (e.g., lowest) layer, such as a physical layer (PHY); l220-2, second (higher) layer, e.g., MAC, RLC, and/or PDCP; l320-3, third (higher) layer, e.g., RRC, non-access stratum, and/or internet protocol; and other layer(s). This type of protocol stack 10 is well known.

In general, the various embodiments of the user device 110 can include, but are not limited to, devices such as smart phones, tablet computers, Personal Digital Assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, internet appliances (including internet of things devices) that allow wireless internet access and possible browsing, tablet computers having wireless communication capabilities, and portable units or terminals that incorporate combinations of such functions.

Each BS/cell 170 provides access to the wireless communication network 100 through a wireless device, such as UE 110. Each BS/cell 170 provides at least one cell and may provide a plurality of cells. The cells form part of a base station. That is, there may be multiple cells per base station. For example, there may be three cells for a single carrier frequency and associated bandwidth, each covering one third of a 360 degree area such that the coverage area of a single base station covers approximately an ellipse or circle. Further, each cell may correspond to a single carrier and a base station may use multiple carriers. So if there are three 120 degree cells and two carriers per carrier, the base station has 6 cells in total. Thus, when discussing serving BS/cell 170-1 and non-serving BS/cell 170-2, these may be two different cells from the same base station, or two different cells from two different base stations.

As used herein, a serving cell is a cell with which UE 110 is exchanging user data, i.e., receiving/transmitting data from/to the cell. In contrast, the non-serving cell may be, for example, one of the following cells.

1) A cell to which the UE is not connected and which has not been prepared in advance, i.e. which does not have a UE context (relevant information about the UE regarding configuration, capabilities, history, etc.).

2) A cell to which the UE is not connected but is prepared, i.e. the cell does have the UE context. Herein, the non-serving cell may be prepared in advance/proactively by the serving cell.

3) The UE is connected to a cell with which it does not exchange any user data. This may correspond to a multi-connection scenario, where the UE is connected to multiple cells but is served by only one or a subset of them at a time.

It is assumed that the two BS/cells 170 are similar and only an example of circuitry in the serving BS/cell 170-1 will be described. The BS/cell 170 may be, for example, a base station for 5G, also referred to as a New Radio (NR), which uses the term "RAN node" to refer to the base station. In 5G, BS/cell 170 may be a NG-RAN node, defined as a gNB or NG-eNB. The gNB is a node providing NR user plane and control plane protocol terminations to UEs and is connected to the 5GC (e.g., network element(s) 190) via an NG interface. The NG-eNB is a node providing E-UTRA user plane and control plane protocol terminations to the UE and is connected to the 5GC via the NG interface. The NG-RAN node may comprise a plurality of gnbs, which may also comprise a Central Unit (CU) (gNB-CU)196 and a Distributed Unit (DU) (gNB-DU), of which DU 195 is shown. Note that the DU may include or be coupled to and control a Radio Unit (RU). The gNB-CU is a logical node hosting the RRC, SDAP and PDCP protocols of the gNB or the RRC and PDCP protocols of the en-gNB, controlling the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connecting with the gNB-DU. The F1 interface is illustrated as reference numeral 198, although reference numeral 198 also illustrates links between remote elements of BS/cell 170 and centralized elements of BS/cell 170, such as links between gNB-CU 196 and gNB-DU 195. The gNB-DU is a logical node of the RLC, MAC and PHY layers hosting the gNB or en-gNB, whose operation is controlled in part by the gNB-CU. One gNB-CU supports one or more cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface 198 to the gNB-CU. Note that DU 195 is considered to include transceiver 160, e.g., as part of an RU, but some examples of this may have transceiver 160 as part of a separate RU, e.g., under control of DU 195 and connected to DU 195. The BS/cell 170 may also be an eNB (evolved node B) base station for LTE (long term evolution) or any other suitable base station. For the eNB, this may use a Remote Radio Head (RRH), also shown at reference 195.

BS/cell 170 includes one or more processors 152, one or more memories 155, one or more network interfaces ((N/WI/F) 161, and one or more transceivers 160 interconnected by one or more buses 157. Each of the one or more transceivers 160 includes a receiver Rx 162 and a transmitter Tx 163. One or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. CU 196 may include processor(s) 152, memory 155, and network interface 161. Note that DU 195 may also contain its own memory/memories and processor(s) and/or other hardware, but these are not shown.

BS/cell 170 includes mobility module 150, which includes one or both portions 150-1 and/or 150-2, which may be implemented in a variety of ways. The mobility module 150 may be implemented in hardware as a mobility module 150-1, such as part of one or more processors 152. The mobility module 150-1 may also be implemented as an integrated circuit or by other hardware, such as a programmable gate array. In another example, the mobility module 150 may be implemented as a mobility module 150-2, which is implemented as computer program code 153 and executed by one or more processors 152. For example, the one or more memories 155 and the computer program code 153 may be configured to, with the one or more processors 152, cause the BS/cell 170 to perform one or more operations as described herein. Note that the functionality of the mobility module 150 may be distributed, such as in the NR between the DU 195 and CU 196, or implemented only in the DU 195.

One or more network interfaces 161 communicate over a network, such as via

links

176 and 131. Two or more RAN nodes 170 communicate using, for example, link 176. The link 176 may be wired or wireless or both and may implement, for example, an Xn interface for 5G, an X2 interface for LTE, or other suitable interfaces for other standards.

The one or more buses 157 may be address, data, or control buses, and may include any interconnection mechanism, such as a series of wires on a motherboard or integrated circuit, an optical fiber or other optical communication device, a wireless channel, or the like. For example, one or more transceivers 160 may be implemented as Remote Radio Heads (RRHs) 195 for LTE or as Distributed Units (DUs) 195 for a gNB implementation of 5G, other elements of BS/cell 170 may be physically different locations than the RRHs/DUs, and one or more buses 157 may be implemented in part as, for example, fiber optic cables or other suitable network connections to connect other elements of BS/cell 170 (e.g., Central Units (CUs), gNB-CUs) to RRHs/DUs 195. Reference 198 also indicates those suitable network link(s).

The wireless communication network 100 may include one or more network elements 190, which may include core network functionality and provide connectivity to additional networks, such as a telephone network and/or a data communication network (e.g., the internet), via one or more links 181. Such core network functions for 5G may include access and mobility management function(s) (AMF (s)) and/or user plane function(s) (UPF (s)) and/or session management function(s) (SMF (s)). Such core network functions for LTE may include MME (mobile management entity)/SGW (serving gateway) functions. These are merely exemplary functions that may be supported by network element(s) 190, and note that both 5G and LTE functions may be supported. BS/cell 170 is coupled to network element (or elements) 190 via link 131. Link 131 may be implemented as, for example, an NG interface for 5G, or an S1 interface for LTE, or other suitable interfaces for other standards. Network element(s) 190 include one or more processors 175, one or more memories 171, and one or more network interfaces ((N/WI/F) 180 interconnected by one or more buses 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and the computer program code 173 are configured to, with the one or more processors 175, cause the network element 190 to perform one or more operations.

The wireless communication network 100 may implement network virtualization, which is a process that combines hardware and software network resources and network functions into a single, software-based management entity, a virtual network. Network virtualization involves platform virtualization, often in combination with resource virtualization. Network virtualization is classified as external, combining many networks or parts of networks into a virtual unit, or internal, providing network-like functionality for software containers on a single system. Note that the virtualized entities resulting from network virtualization are still implemented to some extent using hardware such as

processors

152 or 175 and

memories

155 and 171, and that such virtualized entities also produce technical effects.

The computer-

readable memories

125, 155, and 171 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The computer

readable memories

125, 155 and 171 may be means for performing a storage function. By way of non-limiting example,

processors

120, 152, and 175 may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, Digital Signal Processors (DSPs), and processors based on a multi-core processor architecture.

Processors

120, 152, and 175 may be means for performing functions such as controlling UE 110, BS/cell 170, and other functions described herein.

Having thus described a suitable but non-limiting technical context for the practice of exemplary embodiments of the present invention, exemplary embodiments will now be described in more detail.

The network configures UE 110 with a set of reference signals for monitoring the quality of a radio link (e.g., radio link 111). Note that a "network" refers to at least BS/cell 170 interacting with UE 110 via wireless link 111, but may also include one or more network elements 190. The reference signal set may be referred to as q0 or a beam failure detection reference signal (BFD-RS). Typically, the BFD-RS(s) are configured to be spatially quasi co-located (QCL'd) with PDCCH demodulation reference signals (DMRS), i.e., these reference signals correspond to downlink beams used to transmit the PDCCH. The downlink beam is identified by a reference signal, an SS/PBCH block index or a CSI-RS resource index. The network may configure the BFD-RS list using RRC signaling or with combined RRC + MAC Control Element (CE) signaling.

When the UE is not explicitly configured with a BFD-RS list, the UE shows that BFD-RS resources are determined based on the configured/indicated/activated PDCCH-TCI status of each CORESET, i.e. spatially aligned with PDCCH DMRS (or in other words PDCCH beam) QCL'd downlink reference signals (CSI-RS, SS/PBCH blocks).

The physical layer 20-1 periodically evaluates the quality of the radio link (based on the BFD-RS concentrated by q 0). An evaluation is performed for each BFD-RS and a Beam Failure Instance (BFI) indication is provided to a higher layer (e.g., MAC layer 20-2) when the radio link condition of each BFD-RS in the beam failure detection set is deemed to be in a failure condition, e.g., the hypothetical PDCCH BLER estimated using the Reference Signal (RS) is above a configured threshold. One example of a BLER threshold may be an out-of-sync (in-sync) (OOS) threshold for radio link monitoring, which corresponds to a 10% BLER. The evaluation and indication is performed periodically.

In the event that at least one BFD-RS is not in a failure condition, no indication is provided to higher layers. Meanwhile, the MAC layer 20-2 implements a counter to count BFI indications from the PHY layer and declares a beam failure if the BFI counter reaches a maximum value (configured by the network). The counter may be configured to be supervised by a timer: the timer is started each time the MAC layer receives a BFI indication from a lower layer. Once the timer expires, the BFI counter is reset (the counter value is set to zero).

The network may provide the UE with a list of candidate RSs for recovery that may be indicated using dedicated signals. The candidate beam L1-RSRP measurements may be provided to the MAC layer, which performs selection of a new candidate beam and determines uplink resources to indicate the new candidate to the network. The network may configure the UE with candidate beam-specific dedicated signaling resources (e.g., PRACH resources). That is, the UE may indicate a new candidate beam by transmitting a preamble.

If the UE has declared a beam failure and the UE has detected one or more new candidate beams based on L1 measurements (e.g., L1-RSRP), a beam failure recovery procedure is initiated. Dedicated signals from a PRACH pool, which may be referred to as BFR resources or contention-free random access (CFRA) resources, are configured in a Candidate RS-List in a Candidate-Beam-RS-List, i.e. care has to be taken that the Beam recovery procedure is slightly different from the Random Access (RA) procedure when referring to the response of a base station (e.g. the gNB) to preamble reception. The specific threshold may be configured such that the UE selects any new candidates (based on L1-RSRP measurements) above the threshold for beam failure recovery. In the absence of beams above the configured threshold, UE 110 utilizes contention-based signaling to indicate a new candidate, i.e., contention-based random access (CBRA) preamble resource is mapped to a particular downlink RS.

UE 110 monitors the network response to the Beam Failure Recovery Request (BFRR) during a beam recovery window (similar to the RACH response window) using the same beam alignment used to transmit the recovery signal (i.e., the same beam direction used for TX used for RX). The UE expects the network to provide a response using beams spatially aligned with the indicated downlink reference signals via QCL'd. The case where such correspondence relationship does not hold has not been defined.

When CFRA is used for beam recovery purposes, the UE expects the network to respond with C-RNTI instead of RA-RNTI. In case CBRA resources are used, the UE expects a response from the network, as is typically done in RACH procedures.

Other considerations include Time To Trigger (TTT). The LTE standard supports several parameters to trigger handover and select a target cell, such as hysteresis margin and TTT. When TTT is applied, handover is initiated only if the trigger requirement is met within a time interval defined by the TTT value. This parameter may reduce the number of unnecessary handovers and effectively avoid ping-pong effects, but may also delay handovers, thereby increasing the probability of handover failure.

As additional information about handover, the source configures the UE to report measurements periodically or in an event-triggered manner (i.e., only when a condition is met for a certain duration). For inter-frequency handovers, typically the a3 measurement event is configured, i.e. the UE triggers a report when a neighbor cell becomes more offset than the source/serving cell. See, e.g., 3GPP TS 38.331 or 3GPP TS 36.331.

Each measurement event has an entry condition and an exit condition. In case of an a3 event:

entry conditions were as follows: mn + Ocn > Ms + Off + Hyst; and

leaving conditions: mn + Ocn < Ms + Off-Hyst,

wherein:

ms: measurement of serving cell (L3 filtering);

mn: measurements of neighboring cells (L3 filtering);

and Ocn: cell specific offset i can be configured differently for different neighboring cells;

off: an offset of the handover; and

hyst: hysteresis.

The UE starts a timer with a TTT value if the entry condition is satisfied for the first time. If the timer for the TTT expires, the UE sends a measurement report to the source cell, and this may start the procedure that results in a handover. The timer for the TTT is stopped only if the leaving condition is satisfied. In this case, the UE does not send any measurement report because the timer of the TTT has not expired.

One possible straightforward technique for the beam failure recovery problem that has been examined is for the UE to examine the L1 beam measurements of the source cell and potential target non-serving cells. For example, in an intra-frequency scenario (e.g., mobility between two different cells but within the same frequency in connected mode), if the strongest L1 beam measurement of the source cell is weaker by some offset than the target cell, the UE triggers beam failure recovery to another non-serving cell.

This procedure may limit the cases where beam failure recovery is triggered in the non-serving cell, but does not necessarily reduce unnecessary serving eNB replacement or target cell access failures. This is because the L1 measurement is subject to fast fading fluctuations and measurement errors and is not stable enough to make a reliable decision to trigger beam failure recovery of another serving cell. This can therefore lead to cell changes after fast fading and measurement errors. This needs to be avoided because "false alarms" that can lead to a fast handover back to the source cell or even a failure of the target cell.

T312 has been introduced to declare early RLF in L3 and initiate RRC reestablishment procedure. The network may configure T312 for a certain measurement event X. If a measurement report is triggered from a measurement event X while timer T310 is running, timer T312 starts. If the timer T312 expires, the UE declares RLF and initiates an RRC reestablishment procedure. In the current 3GPP specifications, the timer T312 is started only when T310 is already running, but the proposal to start the timer T312 independently of T310 with triggered measurement reporting has been discussed.

The exemplary embodiment is based on the assumption that: if the target cell is stable enough, it is likely that the RRC measurement event has been triggered shortly before (e.g., but the measurement event based report may be lost). Otherwise, if no measurement report has been triggered in advance, it is likely that the target cell is not stable enough and BFRs to that neighbor are risky and may result in failure or handover back to the serving cell.

As described above, TTT is used to trigger measurement reporting for handover. TTT is also used herein such that beam failure recovery to another cell is only allowed when measurement reporting has been triggered using TTT. Thus, there is an interaction here between measurement reporting for inter-L3 cell mobility and beam failure recovery in non-serving cells.

The exemplary embodiments propose the following for triggering a beam failure recovery procedure in a non-serving cell.

1) The timer T is started when a measurement event for which the timer T is configured triggers a measurement report.

The entry condition for the measurement report event may be evaluated using, for example, the L3 filtered cell quality of the target cell. The quality is currently derived as the average of the N strongest beam measurements above the threshold (or if no beam is above the threshold, the UE uses the best beam).

The measurement report may be triggered when an entry condition is met during a particular time-to-trigger (TTT) or when a timer for the TTT expires. That is, from an implementation point of view, a measurement report is only sent when a timer for the TTT expires. This will only occur if the entry condition has been fulfilled at least once and the exit condition has never thereafter been fulfilled, such that the timer TTT expires.

2) If a beam failure has been detected while the timer is running T, the UE is allowed to initiate beam failure recovery to the strongest non-serving cell or any cell that has met the criteria for starting timer T. Otherwise, UE 110 should perform beam failure recovery only in the same serving cell.

In some embodiments, the UE may be provided with an alternative SSB/CSI-RS candidate set for BFRs (including other configurations) to be applied while the timer T is running. That is, the SSB/CSI-RS candidate set (e.g., including other configurations) for the BFR that is applied while timer T is running may be different from the set that may be used by the UE before timer T is started. For example, before the timer T is started, the SSB/CSI-RS candidate set for BFR contains only candidates from the serving cell, whereas when the timer T is running, the set contains candidates from both the serving (e.g., source) and target cells. Alternatively, the set of SSB/CSI-RS candidates configured for BFR may include candidates from both the source and target cells before timer T is started, and contain only SSB/CSI-RS candidates from the target cell when timer T is running.

3) If the timer T expires, the UE performs beam failure recovery in the same serving cell in which the beam failure was detected.

In the latter case, it can no longer be assumed that the radio conditions of the target cell are sufficiently stable and/or that the entry conditions of the measurement event triggering the reporting will still be fulfilled. The example of the method ends here.

Unlike conventional techniques, the UE is allowed to initiate a MAC beam failure recovery procedure to the non-serving cell in response to the L3 condition for RRC inter-cell mobility being satisfied. This ensures that beam failure recovery is triggered when the radio link of the source cell is no longer sufficient and the radio link quality of the target non-serving cell is stable enough to continue serving the UE once the UE has handed over to the non-serving cell.

When the MAC layer (e.g., 20-2 in fig. 1) in UE 110 detects a beam failure, MAC layer 20-2 may trigger a failure indication to a higher layer (e.g., layer 20-3) to indicate that MAC layer 20-2 has detected a beam failure.

This enables the RRC layer 20-3 to check whether the timer T is running for any cell. If a beam failure indication is received while the timer T is running, the RRC layer 20-3 can instruct the MAC layer 20-2 to initiate beam failure recovery to a particular target cell that has satisfied the entry conditions for the measurement event associated with the timer T. If the RRC layer 20-3 does not perform any action after receiving the indication from the MAC layer 20-2, the UE 110 performs beam recovery for the serving cell as typically performed in accordance with the above.

In yet another option, the MAC layer 20-2 may indicate to higher layers (e.g., 20-3) that a beam failure has been detected and that no serving cell CFRA candidate is above a threshold. This may delay the indication until the CFRA candidate is evaluated.

Fig. 2 depicts an exemplary signaling diagram for the case where a beam failure has been detected while the timer T is running. In this example, the serving BS/cell 170-1 signals a measurement configuration message 210 that includes a measurement report event associated with a timer T. In block 220, the UE 110 determines that an entry condition for the measurement event is met during a time-to-trigger (TTT) or that a timer for the TTT has expired. That is, the non-serving BS/cell 170-2 now meets the criteria for making a HO candidate possible for that cell. Note that the measurement configuration may have a white or black list of cells to be considered in the measurement, and furthermore, it may happen that more than one cell meets the criteria (although this is not a common case). Both cases can be considered simultaneously if necessary. UE 110 starts a timer T and signals a measurement report 230. The serving BS/cell 170-1 may or may not receive the Measurement Report (MR)230, as described in block 235. That is, fig. 2 shows that the measurement report is transmitted by the UE, but does not indicate whether the measurement report is successfully received by the source cell. Such measurement reports may be lost. Rather than declaring a radio link failure after detecting the radio link failure, for example, due to expiration of timer T310, UE 110 may perform beam failure recovery to another cell before expiration of timer T, as shown in fig. 2. For example, when timer T is running, UE 110 detects a beam failure in block 240. A beam failure recovery procedure 250 is performed between UE 110 and target non-serving BS/cell 170-2.

Fig. 2 illustrates one of the examples described in the above overview, where if the target cell is sufficiently stable, it is likely that the RRC measurement event has been triggered shortly before. Assume that the target non-serving BS/cell 170-2 is therefore appropriate for the BFR procedure 250.

Turning to fig. 3, this figure depicts the situation where a beam fault is detected when the timer T is not running. This may correspond to the case where a beam failure is detected when the measured entry condition is being evaluated or even satisfied by the UE but is not satisfied during the TTT. In this case, the timer T is not started and the UE triggers beam failure recovery in the same serving cell. In this example, the serving BS/cell 170-1 signals a measurement configuration message 210 that includes a measurement report event associated with a timer T. In block 320, UE 110 determines that the entry condition for the measurement event has not been met during the TTT or that a timer for the TTT has not expired. Therefore, the timer T is not started. In block 330, the UE 110 detects the beam failure and a beam failure recovery procedure 350 is performed between the UE 110 and the serving BS/cell 170-1.

Figure 3 illustrates one of the examples described in the summary provided above, where if no measurement report has been triggered in advance, it is likely that the target cell is not stable enough and BFRs to the neighbor are risky and may result in failure or handover back. Assume that the target non-serving BS/cell 170-2 is therefore not suitable for the BFR process 250 and the BFR process 350 is instead returned to the serving BS/cell 170-1.

In one embodiment, the existing timer T312 may be reused for the proposed behavior. In an alternative embodiment, the timer/counter associated with RLF detection or BFR is adjusted in response to the UE being allowed to perform a recovery to the non-serving BS/cell 170-2. That is, while the timer T is running, if a beam failure has been detected in the serving cell, the UE is allowed to perform beam failure recovery in another cell, and during this period, the UE may apply a specific value for the timer/counter used for RLF detection or BFR in the target cell. For example, the number of random access trials during the BFR or RACH response window may be different for the serving and target cells.

Fig. 4 is a logic flow diagram of an exemplary process performed by UE 110 for robust beam failure recovery using non-serving cells. The figure illustrates how the UE may implement figures 2 and 3. The figure further illustrates the operation of one or more exemplary methods, the results of execution of computer program instructions embodied on a computer readable memory, the functions performed by logic implemented in hardware, and/or the interconnected components for performing the functions in accordance with the exemplary embodiments. For example, the mobility module 140 may include multiple ones of the blocks in fig. 4, where each included block is an interconnecting component for performing the functions in the block. Assume that the blocks in fig. 4 are performed by UE 110, e.g., at least partially under control of mobility module 140.

In block 405, the UE 110 receives a measurement configuration message 210 that includes the TTT and information for the measurement reporting event and its corresponding association with the timer T. I.e. the association is provided by the network. Note that only one block is shown here, but these may be configured separately, such as the TTT and information being configured via different signaling at different times. One example of a timer that may be used is a timer T312 implemented as a timer T. See block 410.

In block 415, UE 110 determines whether the measured entry condition is met during the TTT or whether a timer for the TTT has expired. If the entry condition is met or the timer for the TTT has expired (yes at block 420), UE 110 starts the timer T in block 425 and sends the measurement report 230 in block 430, and flow proceeds to block 435. Block 433 is an example of another alternative where, depending on the network configuration, a different timer/counter is applied that is related to RLF detection or BFR while timer T is running. Block 434 is an additional alternative in which UE 110 may apply a different set of SSB/CSI-RS candidates for BFR (e.g., including other configurations) while timer T is running than was used before timer T was started.

If the entry condition is not met or the timer for the TTT has not expired (no at block 420), flow proceeds to block 435 where UE 110 determines whether a beam failure is detected. If a beam failure is not detected (no at block 440), if timer T has been started (no at block 440 and timer T has been started), flow proceeds to block 435. Otherwise (block 440 no and timer T has not started), flow proceeds to block 415.

If a beam failure is detected (block 440 — yes), UE 110 determines whether timer T is running in block 445. If the timer T is running (yes at block 450), the UE 110 performs a beam failure recovery procedure with the target non-serving BS/cell 170-2 (block 455). Note that if there are multiple candidate target cells, the UE will select the strongest one. In contrast, if the timer T is not running (no in block 450), the UE 110 performs a beam failure recovery procedure with the serving BS/cell 170-1 in block 460.

Additional examples are as follows.

Example 1. a method, comprising:

determining, by the user equipment and in response to the beam failure being detected for a serving cell serving the user equipment, whether a timer is running; and

performing, by a user equipment, one of the following operations:

a beam failure recovery procedure with a target non-serving cell running in response to a timer; or

A beam failure recovery procedure with the serving cell in response to the timer not running.

Example 2. the method according to example 1, further comprising:

prior to determining whether the timer is running, performing the following:

determining, by the user equipment, whether an entry condition for a measurement event is met during a trigger time or whether a timer for the trigger time has expired, wherein the measurement event is configured at least for the user equipment to measure one or more non-serving cells including the target non-serving cell; and

in response to determining, by the user equipment, that the entry condition for the measurement event is met during the trigger time or that a second timer for the trigger time has expired, starting running of the timer.

Example 3 the method of example 2, further comprising sending a measurement report in response to determining, by the user equipment, that the entry condition for the measurement event has been met during the trigger time or that a second timer for the trigger time has expired, the measurement report being sent to the serving cell and comprising measurements of the one or more non-serving cells.

Example 4. the method according to example 1, further comprising:

prior to determining whether the timer is running,

determining, by the user equipment, whether an entry condition for a measurement event is met during the trigger time or a second timer for the trigger time expires, wherein the measurement event is configured for the user equipment to measure one or more non-serving cells including the target non-serving cell; and

in response to determining, by the user equipment, that the entry condition for the measurement event is not met during the trigger time or that a second timer for the trigger time has not expired, not starting execution of the timer.

Example 5 the method of any of examples 2 to 4, wherein the entry condition for the measurement event being met comprises an L3 condition for inter-radio resource control cell mobility being met.

Example 6. the method of any of examples 1 to 5, wherein the timer is timer T312.

Example 7. the method of any of examples 1 to 6, wherein the serving cell and the target non-serving cell are formed by the same base station.

Example 8. the method of any of examples 1 to 7, wherein the serving cell and the target non-serving cell are formed by two different base stations.

Example 9. the method of any of examples 1 to 8, wherein performing the beam failure recovery procedure with the serving cell in response to the timer not running further comprises: in response to the timer expiring, a beam failure recovery procedure is performed by the user equipment in the same serving cell in response to detecting the beam failure.

Example 10 the method of any of examples 1 to 9, further comprising, while the timer is running, the user equipment applying a different set of synchronization signal/physical broadcast channel blocks, and/or channel state information-reference signal candidates, for beam failure recovery than was used before the timer was started.

Example 11 the method of any one of examples 1 to 10, further comprising, when the timer is running, the user equipment performing beam failure recovery on the target cell in response to detecting a beam failure in the serving cell, and within a period of time during which the timer is running, the user equipment performing applying the specific value for one or more timers and/or counters used in radio link failure detection or beam failure recovery in the target cell.

Example 12 a computer program comprising code for performing a method according to any of examples 1 to 11 when the computer program is run on a computer.

Example 13 the computer program according to example 12, wherein the computer program is a computer program product comprising a computer readable medium bearing computer program code embodied therein for use with a computer.

Example 14. the computer program according to example 12, wherein the computer program is directly loadable into an internal memory of the computer.

Example 15. an apparatus, comprising:

means for determining, by the user equipment and in response to a beam failure being detected for a serving cell serving the user equipment, whether a timer is running; and

means for performing, by a user equipment, one of:

means for performing a beam failure recovery procedure with the target non-serving cell in response to the timer running; or

Means for performing a beam failure recovery procedure with a serving cell in response to the timer not running.

Example 16. the apparatus according to example 15, further comprising:

since the following components are performed before determining whether the timer is running:

means for determining, by the user equipment, whether an entry condition for a measurement event is met during the trigger time or whether a second timer for the trigger time has expired, wherein the measurement event is configured at least for the user equipment to measure one or more non-serving cells including the target non-serving cell; and

means for starting the running of the timer in response to determining by the user equipment that the entry condition for the measurement event is met during the trigger time or that a second timer for the trigger time has expired.

Example 17 the apparatus of example 16, further comprising means for sending a measurement report in response to determining by the user equipment that the entry condition for the measurement event has been met during the trigger time or that a second timer for the trigger time has expired, the measurement report being sent to the serving cell and comprising measurements of one or more non-serving cells.

Example 18. the apparatus of example 15, further comprising:

means for, prior to determining whether the timer is running:

not only for determining, by the user equipment, whether an entry condition for a measurement event is met during the trigger time or a second timer for the trigger time expires, wherein the measurement event is configured for the user equipment to measure one or more non-serving cells including the target non-serving cell; and;

means for not initiating execution of the timer in response to determining, by the user equipment, that the entry condition for the measurement event has not been met during the trigger time or that a second timer for the trigger time has not expired.

Example 19 the apparatus of any one of examples 16 to 18, wherein the entry condition for the measurement event being met comprises an L3 condition for inter-radio resource control cell mobility being met.

Example 20 the apparatus of any one of examples 15 to 19, wherein the timer is timer T312.

Example 21 the apparatus of any of examples 15 to 20, wherein the serving cell and the target non-serving cell are formed by the same base station.

Example 22 the apparatus of any of examples 15 to 21, wherein the serving cell and the target non-serving cell are formed by two different base stations.

Example 23. the apparatus of any one of examples 15 to 22, wherein the means for performing a beam failure recovery procedure with the serving cell in response to the timer not running further comprises: means for performing, by the user equipment, a beam failure recovery procedure in the same serving cell in response to detecting the beam failure in response to expiration of the timer.

Example 24. the apparatus of any of examples 15 to 23, further comprising means for: while the timer is running, the user equipment applies a different set of synchronization signal/physical broadcast channel blocks, and/or channel state information-reference signal candidates for beam failure recovery than was used before the timer was started.

Example 25 the apparatus of any of examples 15 to 24, further comprising means for the user equipment to perform beam failure recovery on the target cell in response to detecting a beam failure in the serving cell when the timer is running, and means for the user equipment to perform applying the specific values for one or more timers and/or counters used in radio link failure detection or beam failure recovery in the target cell within a time period during which the timer is running.

Example 26. an apparatus, comprising:

one or more processors; and

one or more memories including computer program code,

wherein the one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to perform operations comprising:

performing, by a user equipment, one of the following operations:

performing a beam failure recovery procedure with the target non-serving cell in response to the timer running; or

Performing a beam failure recovery procedure with the serving cell in response to the timer not running.

Example 27 the apparatus of example 26, wherein the one or more memories and the computer program code are further configured to, with the one or more processors, cause the apparatus to perform operations comprising:

prior to determining whether the timer is running, performing the following:

Example 28 the apparatus according to example 27, wherein the one or more memories and the computer program code are further configured to, with the one or more processors, cause the apparatus to perform operations comprising: sending a measurement report in response to determining, by the user equipment, that an entry condition for a measurement event has been met during the trigger time or that a second timer for the trigger time has expired, the measurement report being sent to the serving cell and comprising measurements of the one or more non-serving cells.

Example 29 the apparatus of example 26, wherein the one or more memories and the computer program code are further configured to, with the one or more processors, cause the apparatus to perform operations comprising:

prior to determining whether the timer is running, performing the following:

Example 30 the apparatus of any one of examples 27 to 29, wherein the entry condition for the measurement event being met comprises an L3 condition for mobility between radio resource control cells being met.

Example 31 the apparatus of any one of examples 26 to 30, wherein the timer is timer T312.

Example 32 the apparatus of any of examples 26 to 31, wherein the serving cell and the target non-serving cell are formed by a same base station.

Example 33 the apparatus of any of examples 26 to 32, wherein the serving cell and the target non-serving cell are formed by two different base stations.

Example 34 the apparatus of any one of examples 26 to 33, wherein performing the beam failure recovery procedure with the serving cell in response to the timer not running further comprises: in response to the timer expiring, a beam failure recovery procedure is performed by the user equipment in the same serving cell in response to detecting the beam failure.

Example 35 the apparatus of any of examples 26 to 34, wherein the one or more memories and the computer program code are further configured to, with the one or more processors, cause the apparatus to perform operations comprising: while the timer is running, the user equipment applies a different set of synchronization signal/physical broadcast channel blocks, and/or channel state information-reference signal candidates for beam failure recovery than was used before the timer was started.

Example 36 the apparatus of any of examples 26 to 35, wherein the one or more memories and the computer program code are further configured to, with the one or more processors, cause the apparatus to perform operations comprising: when the timer is running, the user equipment performs beam failure recovery on the target cell in response to having detected a beam failure in the serving cell, and within a period of time during which the timer is running, the user equipment applies specific values for one or more timers and/or counters used in radio link failure detection or beam failure in the target cell.

An example 37. a computer program product comprising a computer-readable storage medium bearing computer program code embodied therein for use with a computer, the computer program code comprising:

code for determining, by the user equipment and in response to a beam failure being detected for a serving cell serving the user equipment, whether a timer is running; and

code for performing, by a user equipment, one of:

code for performing a beam failure recovery procedure with a target non-serving cell in response to a timer running; or

Code for performing a beam failure recovery procedure with a serving cell in response to the timer not running.

As used in this application, the term "circuitry" may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) a combination of hardware circuitry and software, such as (as applicable): (i) a combination of analog and/or digital hardware circuit(s) and software/firmware and (ii) any portion of hardware processor(s) with software (including digital signal processor (s)), software and memory(s) working together to cause an apparatus (such as a mobile phone or server to perform various functions) and

(c) hardware circuit(s) and/or processor(s), such as microprocessor(s) or a portion of microprocessor(s), that require software (e.g., firmware) for operation, but may not be present when not required for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As another example, as used in this application, the term circuitry also encompasses implementations in only a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also encompasses, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in a server, a cellular network device, or other computing or network device.

Embodiments herein may be implemented in software (executed by one or more processors), hardware (e.g., application specific integrated circuits), or a combination of software and hardware. In an example embodiment, the software (e.g., application logic, a set of instructions) is maintained on any one of a variety of conventional computer-readable media. In the context of this document, a "computer-readable medium" can be any medium or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer, for example, one example of a computer described and depicted in FIG. 1. A computer-readable medium may include a computer-readable storage medium (e.g.,

memory

125, 155, 171 or other device) that may be any medium or means, such as a computer, that can contain, store, and/or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device. Computer-readable storage media do not include propagated signals

If desired, the different functions discussed herein may be performed in a different order and/or concurrently with each other. Further, one or more of the above-described functions may be optional or may be combined, if desired.

Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described embodiments and/or the dependent claims with the features of the independent claims, and not solely the combined claims explicitly defined.

It is also noted herein that while the above describes example embodiments of the invention, these descriptions should not be viewed in a limiting sense. Rather, various changes and modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

1. A method, comprising:

determining, by a user equipment and in response to a beam failure being detected for a serving cell serving the user equipment, whether a timer is running; and

performing, by the user equipment, one of the following:

a beam failure recovery procedure with a target non-serving cell run in response to the timer; or

2. The method of claim 1, further comprising:

prior to determining whether the timer is running,

determining, by the user equipment, whether an entry condition for a measurement event is met during a trigger time or whether a second timer for the trigger time has expired, wherein the measurement event is configured at least for the user equipment to measure one or more non-serving cells including the target non-serving cell; and

initiating the running of the timer in response to determining, by the user equipment, that the entry condition for the measurement event is met during the trigger time or that the second timer for the trigger time has expired.

3. The method of claim 2, further comprising sending a measurement report in response to determining, by the user equipment, that the entry condition for the measurement event has been met during a trigger time or that the second timer for a trigger time has expired, the measurement report being sent to the serving cell and comprising measurements of the one or more non-serving cells.

4. The method of claim 1, further comprising:

prior to determining whether the timer is running,

determining, by the user equipment, whether an entry condition for a measurement event is met during a trigger time or a second timer for the trigger time has expired, wherein the measurement event is configured for the user equipment to measure one or more non-serving cells including the target non-serving cell; and

not initiate the running of the timer in response to determining, by the user equipment, that the entry condition for the measurement event was not met during the trigger time or that the second timer for the trigger time has not expired.

5. The method according to any of claims 2 to 4, wherein the entry condition for the measurement event being met comprises an L3 condition for inter-radio resource control cell mobility being met.

6. The method according to any one of claims 1 to 5, wherein the timer comprises a timer T312.

7. The method of any of claims 1-6, wherein the serving cell and the target non-serving cell are formed by the same base station.

8. The method of any of claims 1-6, wherein the serving cell and the target non-serving cell are formed by two different base stations.

9. The method of any of claims 1-8, wherein in response to the timer not running, performing a beam failure recovery procedure with the serving cell further comprises: performing, by the user equipment, the beam failure recovery procedure in the same serving cell in response to detecting the beam failure in response to the timer expiring.

10. The method according to any of claims 1 to 9, further comprising applying, while the timer is running, a different set of synchronization signal/physical broadcast channel blocks, and/or channel state information-reference signal candidates, for beam failure recovery than was used before the timer was started.

11. The method according to any of claims 1 to 10, further comprising applying, by the user equipment, specific values for one or more timers and/or counters used in radio link failure detection or beam failure in the target cell during a period of time in which the timer is running.

12. A computer program comprising code for performing the method according to any one of claims 1 to 11 when the computer program is run on a computer.

13. The computer program according to claim 12, wherein the computer program is a computer program product comprising a computer readable medium bearing computer program code embodied therein for use with the computer.

14. The computer program according to claim 12, wherein the computer program is directly loadable into the computer internal memory.

15. An apparatus, comprising:

means for determining, by a user equipment and in response to a beam failure being detected for a serving cell serving the user equipment, whether a timer is running; and

means for performing, by the user equipment, one of:

16. The apparatus of claim 15, further comprising:

means for, prior to determining whether the timer is running:

determining, by the user equipment, whether an entry condition for a measurement event is met during a trigger time or a second timer for the trigger time has expired, wherein

The measurement event is configured at least for the user equipment to measure one or more non-serving cells including the target non-serving cell; and

17. The apparatus of claim 16, further comprising: means for sending a measurement report in response to determining, by the user equipment, that the entry condition for the measurement event has been met during a trigger time or that the second timer for a trigger time has expired, the measurement report being sent to the serving cell and comprising measurements of the one or more non-serving cells.

18. The apparatus of claim 15, further comprising:

means for, prior to determining whether the timer is running:

19. The apparatus according to any of claims 16 to 18, wherein the entry condition for the measurement event being met comprises an L3 condition for inter-radio resource control cell mobility being met.

20. The apparatus according to any one of claims 15 to 19, wherein the timer comprises a timer T312.

21. The apparatus of any one of claims 15 to 20, the apparatus of any one of claims 15 to 19.

22. The apparatus of any of claims 15 to 20, wherein the serving cell and the target non-serving cell are formed by two different base stations.

23. The apparatus of any of claims 15 to 22, wherein the means for performing a beam failure recovery procedure with the serving cell in response to the timer not running further comprises: means for performing, by the user equipment, the beam failure recovery procedure in the same serving cell in response to detecting the beam failure in response to the timer expiring.

24. The apparatus of any one of claims 15 to 23, further comprising means for: while the timer is running, the user equipment applies a different set of synchronization signal/physical broadcast channel blocks, and/or channel state information-reference signal candidates for beam failure recovery than was used before the timer was started.

25. The apparatus according to any of claims 15 to 24, further comprising means for applying specific values for one or more timers and/or counters used in radio link failure detection or beam failure in the target cell during a period of time when the timer is running.

26. An apparatus, comprising:

one or more processors; and

one or more memories including computer program code,

wherein the one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to:

performing, by the user equipment, one of the following:

27. The apparatus of claim 26, wherein the one or more memories and the computer program code are further configured to, with the one or more processors, cause the apparatus to:

prior to determining whether the timer is running,

28. The apparatus of claim 27, wherein the one or more memories and the computer program code are further configured to, with the one or more processors, cause the apparatus to: sending a measurement report in response to determining, by the user equipment, that the entry condition for the measurement event has been met during a trigger time or that the second timer for a trigger time has expired, the measurement report being sent to the serving cell and including measurements of the one or more non-serving cells.

29. The apparatus of claim 26, wherein the one or more memories and the computer program code are further configured to, with the one or more processors, cause the apparatus to:

prior to determining whether the timer is running,

30. The apparatus according to any of claims 27 to 29, wherein the entry condition for the measurement event being met comprises an L3 condition for inter-radio resource control cell mobility being met.

31. The apparatus according to any of claims 26 to 30, wherein the timer comprises a timer T312.

32. The apparatus of any of claims 26 to 31, wherein the serving cell and the target non-serving cell are formed by the same base station.

33. The apparatus of any of claims 26 to 31, wherein the serving cell and the target non-serving cell are formed by two different base stations.

34. The apparatus according to any of claims 26 to 33, wherein in performing a beam failure recovery procedure with the serving cell in response to the timer not running, the one or more memories and the computer program code are further configured to, with the one or more processors, cause the apparatus to: performing, by the user equipment, the beam failure recovery procedure in the same serving cell in response to detecting the beam failure in response to the timer expiring.

35. The apparatus of any of claims 26 to 34, wherein the one or more memories and the computer program code are further configured to, with the one or more processors, cause the apparatus to: applying a different set of synchronization signal/physical broadcast channel blocks, and/or channel state information-reference signal candidates, for beam failure recovery while the timer is running than was used before the timer was started.

36. The apparatus of any of claims 26-35, wherein the one or more memories and the computer program code are further configured to, with the one or more processors, cause the apparatus to: applying specific values for one or more timers and/or counters used in radio link failure detection or beam failure in the target cell during a time period in which the timer is running.

37. A computer program comprising a computer-readable storage medium bearing computer program code embodied therein for use with a computer, the computer program code comprising:

code for determining, by a user equipment and in response to a beam failure being detected for a serving cell serving the user equipment, whether a timer is running; and

code for performing, by the user equipment, one of: